A typical electrophotographic or electrostatograpic reproduction machine employs a photoconductive member that is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charge thereon in the irradiated areas to record an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document.
After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the electrostatic latent image is developed with dry developer material comprising carrier granules having toner particles adhering triboelectrically thereto. However, a liquid developer material may be used as well. The toner particles are attracted to the latent image, forming a visible powder image on the photoconductive surface. After the electrostatic latent image is developed with the toner particles, the toner powder image is transferred to a sheet. Thereafter, the toner image is heated to permanently fuse it to the sheet.
It is highly desirable to use an electrostatic reproduction machine of this type to produce color prints. In order to produce a color print, the electrostatographic reproduction machine includes a plurality of stations. Each station has a charging device for charging the photoconductive surface, an exposing device for selectively illuminating the charged portions of the photoconductive surface to record an electrostatic latent image thereon, and a developer unit for developing the electrostatic latent image with toner particles. Each developer unit deposits different color toner particles on the respective electrostatic latent image. The images are developed, at least partially in superimposed registration with one another, to form a multi-color toner powder image.
The resultant multi-color powder image is subsequently transferred to a sheet. The transferred multi-color image is then permanently fused to the sheet forming the color print. Generally, a color electrostatographic reproduction machine used 4-6 developer units.
In many electrophotographic products, if a developer housing is cycled up but not developing a reasonable amount of toner throughput it tends to cause the materials to degrade which can lead to other xerographic issues (e.g. poor toner developability). The desire is to cycle down one or more developer housings that are not currently needed and will not be needed for some extended period of time to reduce the material degradation. These developer housings need to be cycled back up in time for the next image that requires the particular colorant. The present difficulty is knowing how early to begin the developer housing cycle up and convergence process to ensure the housing(s) is ready in time.
Xerographic cycle up is an ordered sequence of actions necessary to bring the xerographic subsystem to a ready state and is generally accomplished in a predictable amount of time. This is then followed by the “xerographic convergence” process which takes a variable amount of time depending on the current xerographic conditions (e.g. toner age, PR belt age, etc.). To minimize toner material degradation, it is desirable to cycle down any developer housing(s) that will not be used for a certain minimum to be determined (TBD) amount of time. In Xerographic color processes, images are scheduled many seconds (image pitches) into the future. This information could be used to determine the situations when it would be appropriate to cycle down one or more developer housings that will not be needed for the coming job images. A “model” or prediction of the developer housing cycle up and convergence time is needed to ensure the developer housings are brought back online in time for the next image requiring that colorant. Otherwise, productivity will be impacted in the form of skipped pitches waiting for the xerographic subsystem to reach its ready state.